Table 1.

Computerized acoustic analysis variables examined in this study.

Variable	Description	Increasing scores reflect…	Changes to Raw data	Units of Measure
Speech Production
Silence Percent	Percentage of time not speaking	Less percentage of time speaking	None	Percentage
Pause Mean	Average pause length in milliseconds (ms), excluding the first and last pauses.	Longer average pauses	None	Milliseconds
Utterance Number	Total number of utterances (> 150 ms)	More utterances	Computed, per 60,000 milliseconds	Number of Utterances per minute of speech
Utterance Mean	Average utterance length in milliseconds (ms)	Longer average utterances	None	Milliseconds
Speech Variability
Frequency Perturbation	Absolute value of average change in consecutively voiced frames within utterance, averaged across utterances.	Increasing levels of perturbation in F0 signal	None	Semitones
Local Intonation	SD of F0 values computed within each utterance and averaged across all utterances	Higher F0 variability within utterances.	Converted to semitones,	Semitones, per second of average speech
Intensity Perturbation	Absolute value of average change in consecutively voiced frames within utterance, averaged across utterances.	Increasing levels of perturbation in intensity signal	None	Decibels
Local Emphasis	SD of Intensity values computed within each utterance and averaged across all utterances	Higher intensity variability within utterances.	Divided by average utterance length in seconds	Decibels, per second of average speech